PROPAGATION OF FISH.
There is no subject more important to the material welfare of our
country, or that a persistent and willful disregard of the laws of
nature has rendered more necessary, than the culture of the various
tribes of fish that were once abundant in our rivers and lakes and along
our coasts, but which are rapidly diminishing, and threaten soon to
become extinct.
Fortunately great strides have been made and great interest aroused in
this matter, and the only article in the first edition of this work
which the author has felt himself called upon to seriously modify, is
that upon this subject. Then there was not a Fishery Commission in a
single State of the Union, nor was there a skilled fish culturist in the
land, except perhaps Dr. Garlick, who was making experiments out West,
and Mr. Seth Green, who was studying out the spawning habits of fish by
himself, by the side of the forest streams, and laying in stores of
knowledge which were to serve as a foundation for the great
fish-cultural fame that he has since acquired. The author may claim that
his former few pages of advice and instruction may have tended in a
measure to bring about the change, and to give to us State Fishery
Commissions in a great majority of the States, and a National
Commission that has no equal for scientific attainments or practical
work in the world. For the creation of the latter, the author also
claims not merely the influence of his writings, but his assistance as a
member of Congress in getting the law passed which established the
United States Fishery Commission, and placed it under the charge of so
efficient a public officer as Mr. Spencer F. Baird.
At that time there was hardly a word written on the subject in this
country except a pamphlet by Dr. Garlick, and such translations from the
French as described the operations under Prof. Coste, and accounts of a
few limited English experiments. Not a private establishment for the
cultivation and sale of fish on any considerable scale existed, and no
expectation that any large public benefits would ever arise from fish
propagation, was generally felt. Since that time hundreds of books have
been written in this country alone, the time of scientific men has been
devoted to it, fish cultural societies have been formed, and there are
several successful establishments for the hatching and sale of young
fish. In no development of this wonderful country has there been so
remarkable an advance, such a change from darkness to light, such an
elevation of public opinion, as in this matter of the artificial
increase of fish.
The limits of this work will not permit a minute and detailed
description of all the details of fish culture. For an exhaustive
treatise on that subject, the reader is referred to a book called
“Fish-Hatching and Fish-Catching,” which contains in a practical form
all that was known up to the time it was written. But general rules are
given in this chapter which will enable the novice, the farmer, the
gentleman country resident and happy owner of a trout stream, to
largely increase his revenue and his pleasure by recruiting his
preserves and making waste waters, if not to blossom as roses, to
produce a yield of food for the table and sport for the rod.
We shall turn first our attention to trout and salmon culture, which are
so nearly identical that they may be studied together. There are at
present no natural salmon rivers in this country except in Maine, Oregon
and California, the efforts to restock the Merrimac and the Connecticut
having only achieved partial success. It is the present opinion of the
writer that salmon were never regular visitors of the Hudson River, or
that if they were indigenous to it, it was only in very limited numbers.
This opinion was formed from a study of the waters which are not well
adapted to the propagation of that class of fishes. Further south than
New York, salmon were probably never known to go at all.
Under the head of Salmon, may be included the salmon, the trout, the
salmon-trout, otherwise called lake-trout, the whitefish, the grayling,
the fresh-water herring or cisco, and California brook-trout, and the
California salmon. The scientific names of these are, _salmo salar_,
_salmo fontinalis_, _salmo confinis_, _salmo amethystus_, _coregonus
albus_, _thymallus signifer_, and _salmo quinnat_. These are all
essentially alike in their mode of culture, the differences being so
inconsiderable that they may be disregarded for the present. We shall
speak of one for the whole, only occasionally pointing out such
individualities as may be necessary.
They spawn in the autumn and winter, with the exception of the
California salmon, which is earlier, and spawns in summer and first of
autumn; the grayling, a fish of the same race, which has lately been
found to exist in our country, and which spawns in March, and the
California brook-trout which spawns in March and April.
The salmon come in from the sea where they have passed the cold weather,
as soon as the ice breaks up, and keep on all summer long running up
into the fresh water; which alone is adapted to the fructification of
their eggs. Trout, in like manner, pass from the ponds and deep lakes
into the cooler streams, where a constant supply of fresh and lively
water can be obtained; whitefish appear from the depths of the great
lakes and seeking the shallows along shore, select gravelly and rocky
reefs and springy spots to lay their eggs.
Salmon and trout make nests, the female digging out the bottom and
fanning away with her fins and tail the mud and finer sand from the
gravel which she afterward uses to cover her eggs. When these operations
are sufficiently advanced, she is joined by the male and they
simultaneously, with one mutual impulse of amatory passion, deposit the
eggs of the female and milt of the male. Only a certain number of these
are extruded at a single impulse, and are then carefully covered over
with gravel by the female, while the male divides his time between
driving away intruders of his own sex, who would usurp his prerogatives
and devouring such stray eggs as may have escaped the notice of his wife
and been carried down stream by the current. One noticeable peculiarity
of the spawn of this class of fish is, that the moment it falls from the
parent, it adheres to whatever it touches. This is a provision of nature
to enable the parent to cover it over with gravel before it is washed
away, which she does with remarkable skill and care, moving the stones
with her ventral fins and tail for that purpose. It remains fast for the
space of thirty minutes or so, and then becomes loose and is swept away
by the current, a dainty morsel for whatever bird or fish or insect that
comes across it. It is also to be observed that the eggs are heavy and
sink to the bottom like shot; a marked peculiarity of the spawn of the
_salmonidae_, and distinguishing them from those of other varieties.
Several different deposits of spawn are made and covered up in this way,
till often quite a mound of fish eggs and gravel is erected. Such mounds
built by the famous trout of Rangeley and her sister lakes are large
enough to fill a two-bushel basket. The operation of emitting the eggs
is not all done at one time or on one day, it occupies several days. As
soon as the nest is completed, and the father and mother are exhausted
of spawn and milt, they drop back worn out and weakly to the deeper
water or the ocean to recuperate. The eggs are left to themselves
unprotected, except for their gravelly covering.
The enemies of fish life are numerous. The most to be dreaded are eels,
which are difficult to exclude from the troughs, and devour eggs and
young with equal voracity. Seven young trout have been taken from the
stomach of an eel six inches long and no thicker than a fine knitting
needle; they grow as they eat, hiding most cunningly in the sand or
gravel from human eye, and making their way through narrow passages and
small holes that a person would not suspect them of being able to enter.
One half-grown eel will destroy an unlimited number of fry or eggs.
Ducks are equally destructive, thrusting their long bills down into the
nests of spawn, or seizing and swallowing the young; frogs, mice, rats,
fish, many birds, and the larvæ of beetles and devil’s darning needles,
and other water flies before they have developed into the perfect
insects do their share of damage. A very large percentage fail to become
impregnated, the current of water probably washing away the milt of the
male before the sperms could enter the eggs. Mr. Livingston Stone says
that in digging some spawn of the California salmon, deposited by the
parents in the natural manner, in the McCloud River, he found only eight
per cent. vitalized.
For almost thirty days after birth the salmon or trout eats nothing, but
is sustained by the absorption of the stomach or what is more accurately
termed the umbilical sac. All this while, as may be readily understood,
he is awkward and hampered in his movements, an easy prey to any hungry
enemy. Appreciating his position he strives to hide himself during this
period; he crawls into holes and under stones, and often hides so
effectually that when he has been artificially hatched his anxious
foster father, the breeder, never discovers what has become of him,
unless his breeding troughs are well made and free from worm holes. But
in this, his hour of weakness, his enemies never desert him, they stand
by him from first to last. At that stage of his development every
miserable shiner, dace and minnow is his master, a very Giant Despair by
comparison with his feebleness.
If he outlives all these perils and attains a marketable size, man steps
in. Man takes the best and so upsets the equipoise of nature, which up
to that time had by its checks and balances kept all varieties of living
creatures at an established relative proportion. For every salmon he
eats there are ten thousand fewer eggs for the water bugs and the
minnows who will make up the loss out of those which are left. These
embodiments of evil must be fed and grow more diligent in the search for
food, the scarcer it becomes; still man keeps on with net, and spear,
and hook, making yearly larger drafts as the human race increases and
extending his machinery as the prey diminishes; so the whole system of
nature is disarranged. The edible fishes at first diminish, then, as the
process goes on in geometrical ratio they decrease more rapidly, and the
operation becomes accelerated at every step, till the stream or lake
which once abounded with excellent fish is utterly and absolutely
denuded and left sterile, bare and unproductive. The insects have
devoured the last edible fish which man’s greediness has failed to
reach. This has happened with so many of the ponds and water courses of
our country that it is safe to say, fully one-half of the lakes, rivers
and streams throughout the older States, at least, yield nothing of food
for man.
Such a result is no trivial injury to the community. The vast extent of
these stretches of water are but little understood by the people at
large. There are in the State of New York alone six hundred and
forty-seven lakes, with an area of four hundred and sixty-six thousand
four hundred and fifty-seven acres, besides countless smaller ponds, and
miles of river and stream. Fully a quarter of a million of acres of the
public patrimony are thus allowed to go to ruin and decay for the want
of proper knowledge and a little care. It would have been easy to have
protected them; it is a far more serious matter to restore their ancient
productiveness.
Trout are found in all rivers in which salmon can hatch their young, but
as they are not necessarily migratory, they often dwell where salmon
cannot. Trout require a temperature of water never exceeding seventy
degrees. At sixty-eight degrees they begin to suffer; at seventy
degrees, unless there is a strong and broken current to give life to the
water, they die rapidly, and not one will survive a temperature of
seventy-five degrees. It is simply manifest then that the Southern and
Western rivers are not generally inhabitable for trout or salmon. Trout
may be found in the head waters of such as rise in the Alleghany range
of mountains, but salmon can exist in none of them. So also with the
sluggish, muddy rivers of Ohio, Indiana, Illinois, Missouri and the vast
central region of our continent. Throughout the entire section between
the Alleghanies and Lake Superior and the Northern Mississippi, except
in Northern Michigan, no trout are found, and then again not till you
come to the Rocky Mountains. Trout and salmon, except in the matter of
migration, are similar in their habits. The eggs of either may be
hatched in the same boxes, with the same water, in about the same time,
and under the same treatment.
When we speak of the temperature of a pond or river, allowance must be
made for springs to which fish will have recourse, precisely as men
perishing in a room for air, would put their mouths to a knot hole to
breathe. If there are springs enough, trout will live in waters the body
of which reaches a higher temperature than seventy-five. So also, a
strong rush of water as with a cataract or rapids, will enable them to
endure greater heat than they could otherwise stand. Still it is not
safe to subject any of the eastern salmon or trout family to a permanent
temperature higher than sixty-five degrees. Salmon trout suffer most
and die the first, at least when they are confined in a limited space
with a small flow of water.
The first point in fish culture is to obtain the spawning fish in proper
condition, for if the eggs are not mature or ripe, as it is usually
called, not only are they useless, but the effort to extract them will
kill the parent. Fish breeders, who make the cultivation of trout a
business, and there are many in this country, keep on hand in suitable
ponds a supply of large fish. These are taken from the rivers, which
they are ascending to spawn, and are kept over from year to year.
Connected with the ponds in which they are confined, is a raceway, or
long narrow trough which has a gravelled bottom, is covered with boards
to exclude intrusive eyes, and in every way is made as attractive a
nesting spot to the fish as possible. Into this they will proceed of
themselves when they are ready to perform their allotted act of
reproduction, and the breeder awaiting his opportunity, places a net at
the mouth of the race and frightening them in, selects such as are ready
for manipulation.
When in a perfectly ripe condition, the eggs lie free in the ovaries in
the abdomen, and may be extruded by a gentle pressure downward along the
sides of the fish. They are caught in a basin and are vitalized by
coming in contact with the milt from the males, for the fish, male and
female, are stripped indiscriminately into one common receptacle.
Formerly, the practice obtained of having this basin full of water,
under the idea that such arrangement more nearly reproduced the natural
conditions, but subsequent discoveries led to a change of this method.
The ova are fertilized by the spermatozoa of the milt entering through
the micropyle, and it was ascertained that these spermatozoa, little
tadpoles as they appear to be under the microscope, were not fond of
water, and although very active when first emitted, soon perished in it.
They retained their vitality much longer when dropped among the ova in a
comparatively dry state, and this is the method universally pursued at
present. The result of the change was very great; on the earlier plan
not more than one egg in three or four was vitalized, whereas now, fully
ninety-eight per cent. are made capable of producing young.
In selecting a place for trout hatching, it is essential to have one
where the water is at an even low temperature, near to the springs if
possible, and where there is absolute security from muddy drainage or
overflow from rains. The shape of ponds is not important, if the water
is abundant and cold enough.
It is best, if possible, to have ponds so arranged that they can be
entirely drained. This is necessary, sometimes, for cleaning or
repairing them, and changing the fish from one pond to another. If the
slope of the ground is sufficient to permit of such an arrangement, it
will often save much labor in pumping or bailing. The drain pipe may be
of pump logs, tile or pipe of any kind, and should be fixed in the
lowest part of the bottom, or as near it as the level of the ground will
allow. Still better would be a regular flume reaching from the bottom of
the pond to the top. A bulkhead may be put in to raise the water as high
as may be required, and a wire screen the whole size of the flume set a
short distance in front of the bulkhead. This large screen has an
additional advantage, as the larger the screen the less liable it is to
clog up with leaves and moss, and the greater will be the volume of
water passing through it.
Screens may be made of common wire painted with tar, or of galvanized
iron wire. The last is the best, as it will last longest in proportion
to its cost. The screens for keeping the small fry should be of fourteen
threads to the inch, and for one year old fish five or six threads to
the inch. Incline the screens at an angle of forty-five degrees, the top
being farthest down stream. By inclining the screens in this manner, a
greater surface is exposed to the water, than if they were placed
perpendicularly. The sockets should be so made that the screens will fit
tightly, and yet be easily taken out to clean.
A very good screen for two and three-year-olds can be made from strips
of lath, planed, and nailed to a strong frame, with quarter-inch
openings between them. Or, what is better, the slats should be at least
four inches wide, so that if a leaf strikes against them, it will catch
without obstructing the flow of water and lie flat against a single
slat, or, if it reaches over the edge, it will be carried through by the
current striking upon one end. It cannot lap around the slat as it would
if it were smaller. As for the width of the slats from one another, the
point to be guarded against is the fish running their heads through far
enough to strike their eyes which will produce blindness. The distance
they are to be apart will depend consequently, mainly on the size of the
heads of the fish, and as fish grow at different rates of speed, it will
not do to go merely by their age, but for fair sized fish an opening of
about five-eighths of an inch will answer. This refers to the upper
screen, the lower screen, that at the foot of the pond, may be larger,
as the fish are more cautious about descending where they cannot see
their way.
The proportion of males to females in a pond should be about one-half.
Not so many are necessary to fecundate the eggs, and it would be an
advantage in one way to have fewer, since then there would not be so
much fighting in choosing partners, and as all the females do not spawn
at once, one male would be enough to serve several females; but, on the
other hand, the males seem to run out of milt before the females get
through laying their eggs, and towards the close of the season it is
often difficult to obtain males with milt enough to fecundate the eggs;
so that it seems better to have in the pond an equal number of males and
females, thereby giving more chance of saving some of the milt till the
last of the season. The males are very amorous, and will pair again and
again. It very often happens, that some of them die from the exhausting
effects of the season.
The trout will not spawn in the ponds where the bottom consists of large
stones or weeds; but if there is sand or gravel anywhere on the bottom
of the ponds, they will spawn on it. Therefore be careful to have only
the raceway, where the water enters, covered with gravel. In October
this may be washed and cleaned from the weeds which will have grown in
it during the year. As soon as the fish are ready to spawn, they will
ascend from the ponds into the raceway, seeking a place to nest. Then
they are ready to be taken out and the spawn expressed. At the entrance
of the raceway, there should be grooves to receive a frame, on which is
tacked a net of coarse bagging about eight or ten feet long. One corner
of this bag should be narrowed, left unsewn, and tied with a string,
like the mouth of a meal sack. The race should be covered over in
spawning time, as the fish will come under the cover better and are not
so likely to be frightened by any one passing. If there are fifteen
hundred or two thousand fish in the pond, the net may be used every day
in the height of the season, and when the fish become scarce, once in
two or three days.
Indications of spawning having been observed, the covers are put on the
races, and as soon as there are fish in the raceway, the net is gathered
up in one hand and the frame held in the other, in such a position as to
be put in the grooves as quickly as possible, so as to let none of the
fish escape from the race. Go quietly to the spot, and do not walk down
the raceway to get to it, but approach from one side and put the net in
the grooves as quickly as you can. The water running down will swell the
net out to its full length. The covers may be then removed, and with a
stick you may frighten the fish down from the head of the raceway into
the net. As soon as they are all in, the frame may be lifted out of the
water, and the fish are then enclosed in the bag. A tub of water should
be previously brought near the spot, and the end of the net can be
lifted into the tub and untied, when the fish will all fall into the tub
without trouble. Coarse cloth is better for the purpose than netting, as
it can be more easily tacked to the frame, does not hurt the fish so
much, and lasts longer; besides, the water swells it out and holds it
open for the fish to run in better than it would a net, and the fish not
seeing you through the cloth as they would through an open mesh, are not
scared, and do not try to run back up the race.
The fish being now in the tub, must be taken to the hatching house
without any delay. There are probably in the tub some fifteen or twenty
fish, and all the operations must be conducted as quickly as possible,
so that they will not die in the small quantity of water to which they
are confined. So long as the fish lie quiet in the bottom of the tub,
there is sufficient air in the water to sustain them, but as soon as
they come to the surface and try to leap out, it is a sign that the air
is nearly exhausted and the water should be renewed. They will also open
their mouths wide, just as a person would when gasping for air. Trout
will die in a tub out of which the oxygen has been exhausted by their
breathing, more quickly than they would die in a cloudy day if out of
the water entirely.
A fire may be made in the hatching-house to warm your fingers, which
will probably get cool while engaged in this operation. A six-quart
milk-pan is to be provided, if you have many fish, and also another tub
of water, into which to put the fish after they are deprived of their
spawn. Select a fish, and holding it over the milk-pan, which has been
dipped in water to wet it, rub it gently with the fore-finger and thumb,
from the pectoral fins to the vent. A little experience will show how
this is to be done. If the fish is ripe, a few drops of pearly-colored
milt, or orange-hued eggs, will be forcibly expressed in the pan. If the
milt is not of this color, it shows that the milt is not good, and
another male must be taken, and treated in a similar manner. The female
must be pressed more slowly and oftener than the male. If the eggs are
not ripe, by passing the hand lightly over the belly, you will feel them
beneath, hard, like shot. In that case put the fish back into the pond,
for the eggs to ripen. When the eggs are ripe, the belly will be soft
and flabby, and the eggs beneath the skin feel loose and change their
position at the touch. The operation must be continued until the fish
are emptied of eggs and milt. The eggs in the pan may, at intervals, be
gently stirred by moving the pan; this is to change the position of the
eggs, so as to be sure that all come in contact with the milt, and when
the operation is completed, a half-pint of water is poured on them and
the pan set in one of the hatching troughs through which the water is
running; this will keep the eggs up to the proper temperature, and
prevent a sudden change when they are transferred to the trough. The
eggs will now agglutinate or stick to the pan, and to each other, for a
little while.
The fish must be grasped by the head, if you are right-handed, with the
right hand, and by the tail, or rather the lower part of the body, with
the other hand, and held over the pan with the belly near the bottom of
the pan. As soon as the fish is quiet, the right hand may be gently
slipped down from the head, and the fore-finger and thumb used to press
the belly. The fish still being held by the tail, and lower part in the
left hand, and partly supported, perhaps, by the sleeve of the coat, or
by the bare arm, and the remaining fingers of the right hand. The pan
should be elevated at one side, during the operation of taking the
spawn, by standing it on a block half an inch thick, and enough water
will drip from the fish so that by tilting and shaking it, the milt can
be brought in contact with the eggs.
After stripping a female once she should be returned to the tub from
which she was taken, and should be stripped again after a short time,
during which other fish are being handled. This is to get the last egg
from her, and if it is not done a few will remain and she will go on
the spawning beds to deposit them as if she had a full supply. If she is
cleaned entirely, she will not bother herself or her owner about the
matter again that season. The California mountain trout retain their
eggs and milt with more determination than our brook-trout, and must be
humored like a cow that will not give down her milk to any one but the
creature for which nature intended it. After the trout are handled they
are returned to different tubs, according to their sizes, as this is the
occasion to sort them.
Twenty to twenty-five minutes having now elapsed since the pan of eggs
was set in the trough, gently tip up the pan. If the eggs are loose and
roll separately as you move it, they are ready for subsequent
operations; if not yet loose, let them remain a while longer. Pour off
the dirty water until only sufficient is left to cover the eggs. If this
is done very gently, the eggs, although very light, will remain at the
bottom, as they are somewhat heavier than water; then sink the pan into
the water, at the same time tipping it, and take it half full of water.
The influx of water will wash the eggs around somewhat, and dilute the
dirty water remaining in the pan. This is to be poured off, as before,
and the operation repeated, until the water looks perfectly clear. There
will be some dirt and droppings of the trout still left, which can be
carefully picked out with the nippers. If an egg should happen to be
broken, while being taken from the trout, every vestige of it should be
carefully removed, as the slimy, sticky contents will get on the other
eggs and kill them. The eggs are now ready to be placed in the trough,
as soon as you shall have raised the water in the nest to which you wish
to transfer them, by placing a strip across the trough. Then sink the
pan gently to the edge in the water of the trough, at the same time
tipping the pan, so that the water in the trough and in the pan shall
come together with as little current as possible. Then the edge of the
pan may be sunk into the water, and by tipping the pan a little more,
the eggs will flow out without injury. By moving the pan while the eggs
are running out, they may be spread uniformly over the bottom. If they
fall in a heap, take the bearded end of a feather, and move the water
with it in the direction you wish the eggs to go, and they will follow
the current thus created. This may be done without touching the eggs
with the feather. Distribute the eggs as evenly as possible over the
surface of the nest. Where they are placed upon wire sieves, these may
be moved and shaken under water, so as to distribute the eggs evenly.
The strip which was placed across the trough to raise the water, should
then be removed. Care must be taken that it be not removed so suddenly
as to cause a rush of water, which would carry most of the eggs away
with it. Raise the strip a little way from the bottom, so as to let the
water run out gradually, and when it is very nearly or altogether at the
proper level, the strip may be removed entirely. Those who have a
nursery attached to the troughs, place the earliest eggs in the lower
end of the trough, and keep placing them toward the top, so that the
fish which are first hatched can run first into the nursery without
disturbing the others. About ten thousand may be placed in each nest
eighteen inches by fifteen inches.
If the eggs have been received from a trout breeder, they should be left
in the packages in which they have been sent until the troughs are
ready for them. Persons will sometimes take the tin boxes containing the
eggs out of the sawdust in which they were packed, and set them in the
water of their troughs, with the idea perhaps of getting the eggs in the
box to the same temperature as the water before unpacking them. This
will surely kill the eggs in a few hours. Leave them in the original
package until a few hours before you are ready to place them in the
troughs. Then take out the tins and set them over or near the troughs,
which will reduce or raise the temperature enough. Then empty the box
into a tin pan full of water taken from the trough, pick out as much
moss as you can readily with your fingers or nippers, and wash off the
rest in the manner shown in directions for washing eggs hereafter.
The eggs are placed on trays made of wire cloth stretched on wooden
frames. Each tray is twenty-seven inches long by fourteen inches wide,
and will hold in a layer, one deep, six thousand two hundred and
seventy-two salmon trout eggs. Instead of using only one layer of these
trays, it has been the practice of late years to use four layers in the
upper sections and five in the lower sections.
If only a few eggs are to be hatched (say eight or ten thousand) no
hatching house is necessary. The troughs may be placed in the open air,
in any convenient place, and covered with a wire screen, to keep out
rats, mice and ducks. A light board cover must then be laid over them,
to shed the rain and snow and keep the eggs from exposure to the
sunlight. A hatching house is much more comfortable to work in. A stove
may be put in it and a fire started occasionally for warming one’s
fingers, but it is not needed for hatching purposes, as spring water in
these latitudes is warm enough. The house may be constructed of rough
boards, or as expensively as you choose, but care should be taken to
have a water-tight roof, as drops of water leaking through and falling
into the troughs will kill the eggs underneath. Its size must be
regulated by the number and extent of the troughs.
The windows in a hatching house should be few in number and provided
with curtains or shutters, as the sun shining upon the spawn will kill
it. Not that a few minutes’ exposure to the rays of the sun will hurt
the eggs, but a few hours’ exposure certainly will. Perhaps it would be
well to have the windows, if possible, made on the north side of the
hatching house, into which the sun will not shine in the winter season.
Keep the hatching house clean. In fact cleanliness is one of the
cardinal virtues to the trout raiser. He should have a clean house,
should work with clean hands, and have all his pans, spoons and utensils
of every sort free from grease and dirt.
The troughs should be made of seasoned timber, one and a half inch
thick. They should be six inches deep and about fifteen inches wide,
inside measurement. It would be better, perhaps, if the troughs were
eight or nine inches deep, because then the water could be raised higher
over the young trout after they are hatched out. The difficulty in
making them so deep is that when the sides of the trough are made so
wide, they are apt to warp or stretch apart at the top, and must be
stayed in some way; for instance, by strips nailed across. But the
cleaner the trough is of all strips, elbows, or grooves, the better. The
troughs are divided into squares or nests by cross strips set on the
bottom at intervals of eighteen inches. These strips may be made of
half-inch stuff and cut two inches in width. There is no necessity for
nailing them to the bottom; fit them in accurately and set them edgeways
at intervals of eighteen inches. As they do not need to be removed
often, it is better to make them fit tightly. Other strips of the same
stuff must be provided, to fit upon these and made wide enough to raise
the water within an inch of the top of the trough; as these need to be
often moved, they must be made loose enough to take out, and yet fit
accurately enough to raise the water over them when they are put in. New
wood under the action of water develops a slimy sap, therefore it is
necessary to paint the troughs with hot coal tar mixed with enough
turpentine to thin it to about the consistency of paint. The troughs
should have an inclination of about one inch in eight feet--just enough
to let the water ripple gently over the cross strips. They should not be
longer than twenty feet, or the air in the water will be exhausted
before the water reaches the end of the trough. There is more danger of
this after the eggs are hatched out and the troughs are full of young
fish. If possible, the hatching house should be so far below the level
of the spring from which its supply of water is derived, as to allow the
troughs to be raised two or three feet from the floor.
The filter is a box six feet long by one and a half feet wide and one
and one-half feet deep; in which four or five flannel screens can be
placed through which to filter the water before it passes into the
troughs. The coarsest and cheapest red flannel is the best. It will rot
and must be renewed once or twice in a season. Red flannel will last
twice as long as any other. The flannel should be tacked on frames
running in grooves set at an angle of forty-five degrees (the top down
stream), so as to expose as much surface as possible to the water.
Sediment falling on the egg keeps the water off and destroys its life as
effectually as if buried in the mud. If sediment falls upon the eggs it
may be removed by gently agitating the eggs with a feather, or better
still, by creating a current in the water with a feather.
From the filter the water runs into the distributing trough or pipe,
which runs along the head of all the hatching troughs. The water may be
let into the hatching troughs by faucets, or through holes cut into the
trough. These holes should be covered with netting, or the young fish
will run up out of the troughs into the filter, or coarse gravel may be
heaped up at the head of the trough through which the water will run,
but through which the young fish cannot work their way. The supply of
water for one trough should be equal to that coming through a
three-fourth-inch hole with three inches head; just enough to make a
gentle ripple over the cross-pieces. Be careful to get the troughs level
crossways, and the strips true, so that when the water is running it
will form an equal current over every part of each strip along the whole
length of the trough. The length of time required to hatch out the eggs
depends upon the temperature of the water. A general rule sufficiently
accurate for all practical purposes is this: At fifty degrees trout eggs
will hatch out in fifty days, each degree colder takes five days longer,
and each degree warmer five days less. The difference, however,
increasing as the temperature falls, and diminishing as it rises. The
best temperature for hatching is between thirty-five and forty-five
degrees.
After the eggs have lain in the water from fifty to seventy-five days,
according to the temperature, the trout will begin to make their
appearance, the egg appears to be endowed with life, and the motions of
the trout inside “kicking” against the shell to force a way out can be
plainly perceived without the use of a microscope. At length the trout
forces his way through, head first or tail first, those that hatch head
first always dying, however, and the useless shell floats away down
stream. The trout is then about one-half inch long, and the body proper
as thin as a needle; the most prominent features being a pair of eyes,
huge in comparison with the rest of the body, and a sac nearly as large
as the egg. This sac is attached to the belly of the fish, and contains
food, which the fish gradually absorbs. If the fish are hatched in fifty
days, the sac lasts about thirty, if in seventy days, about forty-five.
At this period of their lives they will work down into the crevices of
the gravel and along the sides of the troughs and stay there, nature
seeming to give them the instinct at this weak and defenceless period of
their lives, when they are burdened with a load which they can hardly
carry, to get out of sight and out of the way of harm.
The most critical period in the life of a trout commences when the
umbilical sac is absorbed. More, perhaps, die from the time they begin
to feed until they are six months old, than at any other time. In
consequence many different plans for nurseries have been suggested and
used. The fry require a largely increased supply of water, but where
only a moderate number is to be raised, in place of erecting other and
wider troughs or boxes for nurseries, the better plan is to put only a
few eggs, say five hundred, into each square or nest of the hatching
trough. The square is then large enough with the water raised to keep
the trout well for a month or two after they commence feeding, when they
may be transferred into the first or upper pond.
The fry are removed from the troughs into the pond by the use of a small
net. Take them upon this, a few at a time, and put them into a pan of
water; they will swim off the net and you may draw it from under them.
In the pan they may be carried, a thousand at a time, to the pond in
which you wish to place them. Put them into still water; they will
settle down on the bottom and remain there for some hours, then they
will begin to explore their new quarters, and in a few days will become
thoroughly habituated to the place.
The best food for trout fry is raw liver, chopped as fine as possible,
and then rubbed through a screen or sieve with a flat stick. It must be
reduced to the consistency of pulp, and contain no strings or gristle. A
chopping machine is made for chopping hash or sausage, and either that,
or a couple of sharp knives are used to chop the liver. What is used is
mixed with water so as to reduce it to about the thickness of cream. A
teacupful of this mixture will feed a hundred thousand fish when they
first begin to feed. The best way to feed them is to take a case-knife,
dip it in the food and “slirt” off what adheres into the troughs; a very
simple way, but one answering all practical purposes. Care should be
taken not to feed too much, else the surplus food will remain on the
bottom, and decaying there foul the trough. The reason of the difficulty
in raising young fish appears to be that they are literally starved to
death. The food which we can give them is not natural to them, it is
often given in such coarse pieces that they cannot take it, and
sometimes, through the carelessness of a hired hand, they are neglected
two or three days at a time.
Young salmon, young salmon trout, California mountain trout, and above
all young California salmon are larger, have stronger appetites, and
will accept coarser food. For them, although at first the liver should
be made as fine as for trout, when they are a few weeks old it will be
hardly necessary to dilute it at all, and in the course of a few months
they will not only take the larger pieces, often tearing them apart, but
will scorn the finer portion. At one time sour milk was almost
exclusively used for feeding young fish, but it has been given up. Other
foods have been tried, but with no better success. The fish will not
thrive on any of them as well as they do on liver, and do not thrive on
that as well as if it were a natural food. Near the salt water, where
soft clams can be obtained, they are used in place of liver.
As they grow older, other things may be substituted or may be added to
it as a change. They are fond of the roe of other fish, of the spawn of
the horse-foot or king-crab; of fish itself, and when they are large
enough to eat minnows, no better food can be given them. Liver is too
expensive when it has to be used alone for grown fish, and beef lights
are usually added to it or used in place of it in a measure. It is
miserable food, however, much of it passing through the stomachs of the
trout and salmon wholly undigested and collecting in the bottom of the
ponds. It injures the digestive organs and must be deleterious to the
health of the fish. Its only recommendation is that it is cheap. Maggots
are bred on spoilt meat, hung over the ponds, and as they fall off and
drop into the water are readily devoured, and make excellent food. Or a
piece of spoilt meat may be placed in a deep bottle like a preserving
bottle, and the flies that will collect in immense numbers during summer
may be caught and emptied into the water. This trap will take many times
its bulk of flies being kept set all the time and emptied when any one
is passing it. Flies are probably the best food that can be given to
trout.
Shad eggs differ essentially from trout eggs and require wholly
different manipulation. They are much smaller and lighter. If a trout or
salmon egg is dropped into water it sinks at once to the bottom, but a
shad egg will almost float, and has but little more specific gravity
that the water itself. Shad eggs are less than half the size of trout
eggs, and require as their best condition for hatching a temperature of
from sixty-five to seventy-five degrees. They will hatch at a lower
temperature, but in such cases mature slowly, while eighty degrees of
heat is as much as they can endure. When experiments were first made in
their artificial propagation, they were placed in ordinary trout
troughs, and much trouble was found in their management. If a current of
water was turned on to the same extent as with trout, they all washed
over the end of the troughs, while if the supply was diminished so that
they retained their places, they died of suffocation. It was only after
many different devices had been tried that the proper invention was
discovered--a simple box with the bottom knocked out and replaced by a
wire gauze netting. This box is suspended by floats of wood nailed on
the sides, so that the bottom is presented at an angle to the current,
the degree of inclination being determined by the velocity of the
current. The water striking against the screen enters the minute
interstices, and lifting the eggs, keeps them in gentle motion like the
bubbles of air in a pot of moderately boiling water. All that is
necessary is to attach these boxes one behind the other in a long row,
anchor them in the river, and fill them with impregnated spawn, and the
work is done. The continuous motion of the water passing around each egg
and holding it suspended, aerates it perfectly and makes its hatching a
certainty. Hardly one per cent. of healthy eggs fail to hatch, and while
the process is going on hardly any care or attention is required. Fish
and eels cannot enter the boxes to prey, nor can the eggs be driven out
by the water, and lost.
In the artificial manipulation of shad the parents are taken in seines
from their spawning beds. The haul is made at night, at which time only
can ripe fish be found in any considerable number. The captured fish are
thrown indiscriminately into a boat and are stripped at once as they die
quickly. They are afterwards sold in the markets. The eggs, which are
caught in a pan with a little water in it, after being allowed to stand
for a few minutes until impregnation is complete, which is signified by
their swelling in size and reducing the temperature of the water some
ten degrees, are poured into the hatching boxes and left to themselves.
Nothing more is required. In twenty-four hours the black eyes of the
young fry will be visible through the shell, and in from three to ten
days they will be hatched.
Black bass is one of the most prolific varieties of our fresh-water
fish. Their natural increase is so great and their growth so rapid, that
it has never been an object to fish culturists to attempt their
artificial propagation. When the spawning season draws near, they
select, guided by natural instinct, with great care for the purpose of
propagation, certain portions of the river having a pebbly or gravelly
bottom. From these they remove carefully all sediment, weeds, and
sticks. This work completed, leaves a clear bright space in the bottom
of the river, circular in form, and having a diameter of about three
feet. These beds are readily distinguished by the casual observer from
the ordinary bottom of the river by their brightness, the gravel having
the appearance of being washed or scoured. When the parent fish are
ready to spawn, the female goes upon this prepared bed and deposits her
spawn in a glutinous band or ribbon, running in various directions
across the bed. She is followed by the male who impregnates the eggs by
the expression of his milt.
Their care of the young (the exercise of which is peculiar to the bass,
sunfish, and catfish), taken in connection with the fact that a large
pair of bass will deposit twenty thousand eggs, will give some idea of
their fertility. Possibly the fish are capable of reproduction when two
years old, having at that time attained the extraordinary length of
eight or nine inches, but this is mere conjecture, based more
particularly upon our knowledge of the size and weight of the fish at
that age. They frequently attain the weight of five and six pounds; in
rare instances seven and eight. They are unsurpassed in flavor by any of
the perch family.
The black bass loves bright, pure, lively water, not as cold as the
trout streams of our spring-producing hills and mountains, but free from
foul matters held suspended in it, and with motion either of current or
from the winds. It deposits its eggs on rocky or pebbly ledges. The
parents guard and protect their nests till the young are hatched, and
even watch over the latter till they can take care of themselves. The
fish generally selected for transfer are from one to three years old,
measuring from three to twelve inches in length. Fish of this size are
not only more numerous, but they bear transportation better, and are
more readily acclimated than when larger. They are moved with a great
deal of difficulty in hot weather, especially when the journey requires
more than twelve or fifteen hours; but with care and skill no serious
loss need take place.
The implements of the fish-culturist are few and simple. A few feathers
may be kept on hand to use in spreading the eggs when placing them in
the troughs, in collecting them for packing, and moving them in the
search after dead eggs. Nippers made of wire or some elastic wood, like
red cedar, bent or cut into the shape of the letter U, elongated to
about six inches, and with loops of wire at the ends about the eighth of
an inch wide, will hold an egg without trouble. A small homœopathic
phial is used to examine the eggs. The manner of its use is, to fill it
with water, put in the eggs to be examined, cork it, hold it up before
the window in a horizontal position, and with your microscope look up
through the side of the phial. This brings the egg which lies at the
bottom of the glass within the focus of the microscope, and the water
does not distort its shape. The microscope need not be very strong; one
magnifying eight or ten diameters is amply sufficient. A small net will
be of use in removing the young fish and any refuse in the water from
the troughs; it should be about six inches in diameter, in the shape of
the letter D, with the handle on the middle of the bend. It is very
easily made by bending a wire in the desired shape, and twisting the two
ends together for a handle. Thin gauze of some kind, like bobinet,
should be spread over the wire so tightly that the middle of the net
shall hang only a half inch below the level. An iron spoon, well tinned
or silvered, is used to remove the eggs. Some six-quart tin milk-pans
will be necessary, for a variety of purposes. Eggs may be counted most
easily by measuring them. For this purpose take any small glass, such as
a very small tumbler, for instance, count out five hundred or a thousand
eggs, and with a file make a mark upon the glass as high as they reach,
and the measure is always ready to your hand.
A watering pot with a fine rose spout is used to wash sediment from the
eggs on the sieves, and a broom of twigs is used to brush the screens of
wire.
One of the most curious and interesting results of fish-culture has been
the production of hybrids, some of which were reproductive and have thus
created new species. Strange as it may seem, these experiments have
rarely been wholly abortive; no matter how dissimilar the families, the
eggs have been impregnated often to a large percentage, and have
hatched. The following varieties have been crossed:
FEMALE. MALE.
Salmon-trout with White-fish.
“ “ “ Brook-trout.
Brook-trout “ Fresh-water Herring.
“ “ “ California Salmon.
“ “ “ Mountain-trout.
Shad “ Striped Bass.
“ “ Herring.
It is observable of all hybrids that they are shy and wild; more so
usually than either of their parents, and that in appearance they favor
their larger parent. The cross between the brook-trout and lake-trout
has been repeated from year to year, till fish which are one-eighth
salmon-trout and seven-eighths brook-trout have been produced which it
is hoped will have the size and toughness of the mother, with the beauty
and gameness of the father.
These experiments commenced with a cross of the brook-trout and
California salmon, which had an interesting and instructive termination,
and prepared the way by its failure for subsequent successes.
In September, 1879, the young of the brook-trout and California salmon
were seen to be maturing their eggs. This was the first time in the
history of fish culture that hybrids gave evidence of breeding. It is
asserted that among animals, mules are occasionally known to produce
young, but this is a most unusual exception to a general rule. No more
was expected from the experiments in crossing varieties than the
production of combinations which might be valuable in themselves, like
the capons among fowls, or the mules among draught animals, but which
must of necessity be purely ephemeral, and perishing with the lives of
the individuals. But when these hybrid trout-salmon were opened and
found to contain eggs quite large and well forward in maturity, it
seemed possible that new species might be created and made permanent.
The eggs were already larger than the mature eggs of the trout, although
it was then early in the season, and seemed perfectly healthy. As time
passed the parents were watched with care, and were soon seen to be
going into the spawning-race. They apparently made all their
preparations for spawning, began digging their nests, stayed about them,
and proceeded in the regular way, except that they were never in pairs,
but always single. This was not natural, and led to a careful
examination of them individually. After examining some fifty out of the
sixty, the conclusion was reached that they were all females, which
eventually turned out to be the case. This was in the latter part of
November, 1879. Some dozen male brook-trout were then placed among the
hybrids, to see if they would induce the latter to spawn. Everything
soon appeared favorable for this result, the trout paired with the
trout-salmon, they entered the race-way together, and occupied
themselves with parental duties, but no results were perceived. For some
reason the spawn was not deposited. Then some of the fish were selected
to be stripped by hand, and were found to be ripe, but the eggs were all
crushed in passing from them. The vent of the ovaries or ovaduct was too
small to allow the eggs, which had delicate shells, to pass. Attempts
were then made to enlarge the vent, and some thousands of eggs were
finally obtained in this way uninjured. To impregnate these the milt of
the male trout was used. The parent fish were left in their pond and
seemed to be uneasy. They were doubtless incommoded by the eggs which
they could not pass, and moved about slowly with their heads towards the
bottom, their tails upward, and their bodies at an angle to the surface.
The eggs which it was hoped might be impregnated by hand, were retained
until January 25, 1880, when it was found they were unimpregnated and
dead, and they were thrown away.
Thus two extraordinary facts were ascertained, one that the eggs may be
too large for extrusion in case the male parent is the larger variety of
fish, and the other that the entire body of one hatching may be of a
single sex as in this case when all were females, and in the case of the
shad and herring in the Hudson River, which are all said to be males. It
was on these two discoveries that subsequent improvements were founded.
It is not yet positively determined that these cross-breeds will
procreate their species in a natural way, nor even that they will be the
improvement, which has been hoped, but that they can be bred
artificially there is no further doubt.
An indirect result of fish-culture has been the introduction of foreign
fish into home waters. The German carp has been brought to America, and
has increased and multiplied vastly, and been found well adapted to
certain waters, which are not valuable for finer fish. In dull, muddy,
small ponds, they have not only lived, but they have grown to a
remarkable size. We have also received some German trout, which hatched
and grew well, and which promise finely for the future. Then we have
sent our black-bass to Europe as well as our trout, the California trout
and salmon. We have acclimated in California the Eastern shad, and
imported from California the trout and salmon of that country. This
interchange has been mutually advantageous and promises to be much more
so in the future. The results of fish-culture have indeed far exceeded
the most sanguine hopes of those who first took it up, and at present
there seem to be no limits to its beneficial effects. The time will
surely come when the streams, which have been so long utterly
depopulated of their natural inhabitants will once more be restocked and
yield as abundantly as ever. This has already happened with the
Connecticut River, which from having been almost exhausted, has been so
successfully restocked that it produced in one year more shad than had
ever been caught from it since records had been kept. The Hudson River
had been also rendered nearly worthless as a shad river when
fish-culture was first applied to it, the nets were being taken up and
the fisheries abandoned, the price of even small shad had risen so as to
exclude them from all but the tables of the rich, whereas now the yield
is nearly as numerous as ever, and much larger fish are taken. So while
neglected Southern rivers are exhausted, the Northern ones are being
replenished. The same will follow with the fresh waters. If the trout
brooks have become too warm from the destruction of the forests, other
varieties, such perhaps as the California trout will be substituted.
There are millions of just such streams and ponds, which are now nearly
valueless, but which could be made quite as valuable as the same amount
of land. These will yet all be replenished till the streams and ponds
will come to be regarded as the most valuable part of the farm or
country place, and millions of property will be added to the wealth of
the country.[18]
[Illustration: LARGE-MOUTHED BLACK BASS. (_Grystes Salmoides_)]
[Illustration: FLIES.]